太陽電池と組み合わせることで、光合成を利用せず、光合成より4倍も効率的な植物栽培法が開発されたよ。 by 彩恵りり[@Science_Release]

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科学ライター、彩恵りり[@Science_Release]さんのツイートより。

ちなみに元ネタ記事はnature誌の『A hybrid inorganic–biological artificial photosynthesis system for energy-efficient food production』より。

 

 

◆A hybrid inorganic–biological artificial photosynthesis system for energy-efficient food production
【Nature Food　2022年6月23日】

Abstract

Artificial photosynthesis systems are proposed as an efficient alternative route to capture CO2 to produce additional food for growing global demand. Here a two-step CO2 electrolyser system was developed to produce a highly concentrated acetate stream with a 57% carbon selectivity (CO2 to acetate), allowing its direct use for the heterotrophic cultivation of yeast, mushroom-producing fungus and a photosynthetic green alga, in the dark without inputs from biological photosynthesis. An evaluation of nine crop plants found that carbon from exogenously supplied acetate incorporates into biomass through major metabolic pathways. Coupling this approach to existing photovoltaic systems could increase solar-to-food energy conversion efficiency by about fourfold over biological photosynthesis, reducing the solar footprint required. This technology allows for a reimagination of how food can be produced in controlled environments.

Main

Food demand is growing globally, but food production is ultimately constrained by the energy conversion efficiency of photosynthesis. Most crop plants can convert sunlight and CO2 into plant biomass at an energy conversion efficiency of only ~1% or less1. Large tracts of land are thus required for crop cultivation to capture the requisite solar energy to provide food for humanity. Recent breeding and genetic engineering efforts to increase photosynthetic efficiency have yielded only select gains in a limited number of food crops2,3,4. Increasing the energy efficiency of food production (solar-to-biomass conversion) would allow for more food to be produced using less resources.

Artificial photosynthesis seeks to overcome the limitations of biological photosynthesis, including low efficiency of solar energy capture and poor carbon dioxide reduction, and could provide an alternative route for food production. Recent studies have demonstrated systems that convert CO2 and H2O into reduced species, such as CO, formate, methanol and H2, through electrolysis processes. CO2, CO and H2 can be upgraded to fuels and chemicals through gas-phase fermentation by select bacteria5,6,7; however, gas–liquid mass transfer limits the volumetric efficiency and results in uneconomic fermentation systems. The use of formate or methanol as a carbon source for fermentation is limited because formaldehyde, a toxic intermediate, is formed during biological metabolism of these substrates8,9,10. To date, electrochemically derived substrates cannot support the growth of most food-producing organisms11. However, acetate is a soluble, two-carbon substrate that can be electrochemically produced12 and is more readily metabolized by a broad range of organisms. The use of acetate produced from CO2 electrolysis to cultivate food-producing organisms could allow food production independent of biological photosynthesis but has not yet been demonstrated.

Here we describe the development of a hybrid inorganic–biological system for food production. A two-step electrochemical process converts CO2 to acetate, which serves as a carbon and energy source for algae, yeast, mushroom-producing fungus, lettuce, rice, cowpea, green pea, canola, tomato, pepper, tobacco and Arabidopsis (A. thaliana) (Fig. 1). Coupling this system of carbon fixation to photovoltaics offers an alternative, more energy-efficient approach to food production.

 

 

◆Artificial photosynthesis can produce food without sunshine
Scientists are developing artificial photosynthesis to help make food production more energy-efficient here on Earth, and one day possibly on Mars
【University of California, Riverside：Holly Ober　2022年6月23日】

Photosynthesis has evolved in plants for millions of years to turn water, carbon dioxide, and the energy from sunlight into plant biomass and the foods we eat. This process, however, is very inefficient, with only about 1% of the energy found in sunlight ending up in the plant. Scientists at UC Riverside and the University of Delaware have found a way to bypass the need for biological photosynthesis altogether and create food independent of sunlight by using artificial photosynthesis.

The research, published in Nature Food, uses a two-step electrocatalytic process to convert carbon dioxide, electricity, and water into acetate, the form of the main component of vinegar. Food-producing organisms then consume acetate in the dark to grow. Combined with solar panels to generate the electricity to power the electrocatalysis, this hybrid organic-inorganic system could increase the conversion efficiency of sunlight into food, up to 18 times more efficient for some foods.

“With our approach we sought to identify a new way of producing food that could break through the limits normally imposed by biological photosynthesis,” said corresponding author Robert Jinkerson, a UC Riverside assistant professor of chemical and environmental engineering.

In order to integrate all the components of the system together, the output of the electrolyzer was optimized to support the growth of food-producing organisms. Electrolyzers are devices that use electricity to convert raw materials like carbon dioxide into useful molecules and products. The amount of acetate produced was increased while the amount of salt used was decreased, resulting in the highest levels of acetate ever produced in an electrolyzer to date.

“Using a state-of-the-art two-step tandem CO2 electrolysis setup developed in our laboratory, we were able to achieve a high selectivity towards acetate that cannot be accessed through conventional CO2 electrolysis routes,” said corresponding author Feng Jiao at University of Delaware.

Experiments showed that a wide range of food-producing organisms can be grown in the dark directly on the acetate-rich electrolyzer output, including green algae, yeast, and fungal mycelium that produce mushrooms. Producing algae with this technology is approximately fourfold more energy efficient than growing it photosynthetically. Yeast production is about 18-fold more energy efficient than how it is typically cultivated using sugar extracted from corn.

“We were able to grow food-producing organisms without any contributions from biological photosynthesis. Typically, these organisms are cultivated on sugars derived from plants or inputs derived from petroleum—which is a product of biological photosynthesis that took place millions of years ago. This technology is a more efficient method of turning solar energy into food, as compared to food production that relies on biological photosynthesis,” said Elizabeth Hann, a doctoral candidate in the Jinkerson Lab and co-lead author of the study.

The potential for employing this technology to grow crop plants was also investigated. Cowpea, tomato, tobacco, rice, canola, and green pea were all able to utilize carbon from acetate when cultivated in the dark.

“We found that a wide range of crops could take the acetate we provided and build it into the major molecular building blocks an organism needs to grow and thrive. With some breeding and engineering that we are currently working on we might be able to grow crops with acetate as an extra energy source to boost crop yields,” said Marcus Harland-Dunaway, a doctoral candidate in the Jinkerson Lab and co-lead author of the study.

By liberating agriculture from complete dependence on the sun, artificial photosynthesis opens the door to countless possibilities for growing food under the increasingly difficult conditions imposed by anthropogenic climate change. Drought, floods, and reduced land availability would be less of a threat to global food security if crops for humans and animals grew in less resource-intensive, controlled environments. Crops could also be grown in cities and other areas currently unsuitable for agriculture, and even provide food for future space explorers.

“Using artificial photosynthesis approaches to produce food could be a paradigm shift for how we feed people. By increasing the efficiency of food production, less land is needed, lessening the impact agriculture has on the environment. And for agriculture in non-traditional environments, like outer space, the increased energy efficiency could help feed more crew members with less inputs,” said Jinkerson.

This approach to food production was submitted to NASA’s Deep Space Food Challenge where it was a Phase I winner. The Deep Space Food Challenge is an international competition where prizes are awarded to teams to create novel and game-changing food technologies that require minimal inputs and maximize safe, nutritious, and palatable food outputs for long-duration space missions.

“Imagine someday giant vessels growing tomato plants in the dark and on Mars—how much easier would that be for future Martians?” said co-author Martha Orozco-Cárdenas, director of the UC Riverside Plant Transformation Research Center.

Andres Narvaez, Dang Le, and Sean Overa also contributed to the research. The open-access paper, “A hybrid inorganic–biological artificial photosynthesis system for energy-efficient food production,” is available here.

The research was supported by the Translational Research Institute for Space Health (TRISH) through NASA (NNX16AO69A), Foundation for Food and Agriculture Research (FFAR), the Link Foundation, the U.S. National Science Foundation, and the U.S. Department of Energy. The content of this publication is solely the responsibility of the authors and does not necessarily represent the official views of the Foundation for Food and Agriculture Research.